E-Cigarettes: A Review of New Trends in Cannabis Use

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E-Cigarettes: A Review of New Trends in Cannabis Use

The emergence of electronic cigarettes (e-cigs) has given cannabis smokers a new method of inhaling cannabinoids. E-cigs differ from traditional marijuana cigarettes in several respects. First, it is assumed that vaporizing cannabinoids at lower temperatures is safer because it produces smaller amounts of toxic substances than the hot combustion of a marijuana cigarette. Recreational cannabis users can discretely “vape” deodorized cannabis extracts with minimal annoyance to the people around them and less chance of detection. There are nevertheless several drawbacks worth mentioning: although manufacturing commercial (or homemade) cannabinoid-enriched electronic liquids (e-liquids) requires lengthy, complex processing, some are readily on the Internet despite their lack of quality control, expiry date, and conditions of preservation and, above all, any toxicological and clinical assessment. Besides these safety problems, the regulatory situation surrounding e-liquids is often unclear. More simply ground cannabis flowering heads or concentrated, oily THC extracts (such as butane honey oil or BHO) can be vaped in specially designed, pen-sized marijuana vaporizers. Analysis of a commercial e-liquid rich in cannabidiol showed that it contained a smaller dose of active ingredient than advertised; testing our laboratory-made, purified BHO, however, confirmed that it could be vaped in an e-cig to deliver a psychoactive dose of THC. The health consequences specific to vaping these cannabis preparations remain largely unknown and speculative due to the absence of comprehensive, robust scientific studies. The most significant health concerns involve the vaping of cannabinoids by children and teenagers. E-cigs could provide an alternative gateway to cannabis use for young people. Furthermore, vaping cannabinoids could lead to environmental and passive contamination
The emergence of electronic cigarettes (e-cigs) has given cannabis smokers a new method of inhaling cannabinoids. E-cigs differ from traditional marijuana cigarettes in several respects. First, it is assumed that vaporizing cannabinoids at lower temperatures is safer because it produces smaller amounts of toxic substances than the hot combustion of a marijuana cigarette. Recreational cannabis users can discretely “vape” deodorized cannabis extracts with minimal annoyance to the people around them and less chance of detection. There are nevertheless several drawbacks worth mentioning: although manufacturing commercial (or homemade) cannabinoid-enriched electronic liquids (e-liquids) requires lengthy, complex processing, some are readily on the Internet despite their lack of quality OPEN ACCESS
Int. J. Environ. Res. Public Health 2015, 12 9989 control, expiry date, and conditions of preservation and, above all, any toxicological and clinical assessment. Besides these safety problems, the regulatory situation surrounding e-liquids is often unclear. More simply ground cannabis flowering heads or concentrated, oily THC extracts (such as butane honey oil or BHO) can be vaped in specially designed, pen-sized marijuana vaporizers. Analysis of a commercial e-liquid rich in cannabidiol showed that it contained a smaller dose of active ingredient than advertised; testing our laboratory-made, purified BHO, however, confirmed that it could be vaped in an e-cig to deliver a psychoactive dose of THC. The health consequences specific to vaping these cannabis preparations remain largely unknown and speculative due to the absence of comprehensive, robust scientific studies. The most significant health concerns involve the vaping of cannabinoids by children and teenagers. E-cigs could provide an alternative gateway to cannabis use for young people. Furthermore, vaping cannabinoids could lead to environmental and passive contamination. Keywords: cannabis; vaping; electronic cigarette; adolescence 1. Introduction 1.1. Context There are countless ways to consume cannabis. Means of administration are only limited by the imagination of manufacturers, resellers, and users, and by the technology of the devices used for administration. However, inhalation remains the most popular method of cannabis consumption. Instead of traditional marijuana cigarettes (i.e., cannabis joints), the electronic cigarette (e-cigs) has emerged as the best option for those who are fond of new technological gadgets [1]. It is claimed that e-cig aerosol contains fewer harmful chemicals than ordinary tobacco cigarettes and possibly than regular marijuana cigarettes [2,3]. Gostin’s paper [4] on nicotine vaping and youth raises new issues about e-cigs and their potential misuse for consuming cannabis and other psychoactive drugs. 1.2. E-cigarette Hardware Vaping nicotine using e-cigs differs from smoking regular tobacco cigarettes in many ways. Early, first-generation e-cigs were usually designed to simulate smoking regular tobacco cigarettes; they were low-tech vaporizers with a limited number of settings [1]. Second-generation e-cigs and third-generation modified e-cigs (mods) use more advanced technology; they have atomizers (i.e., heating coils that convert e-liquids into vapor) which improve nicotine dispersal and house high capacity batteries [5]. Cartomizers are similar in design to atomizers; their main difference is a synthetic filler material wrapped around the heating coil. Clearomizers are now very widespread and similar to cartomizers, however they include a clear tank of a larger volume and no filler material; additionally they have a disposable head containing the coil(s) and wicks. Figure 1 shows a diagram and picture of a typical e-cig equipped with a clearomizer. The coils can be fitted to the top of the tank (as in Figure 1), with long wicks hanging down into the tank or at the bottom of the tank with short wicks. E-cigs with advanced
Int. J. Environ. Res. Public Health 2015, 12 9990 technology that includes a large number of settings and the possibility of replacing some critical parts are best suited to cannabis vaping. Figure 1. Microprocessor-controlled, variable-voltage/wattage, personal electronic-cigarette with LED digital display (volts or watts, puff count, ohmic resistance), equipped with a transparent clearomizer and changeable dual-coil head. Vaping cannabis requires an e-cigarette model of this type, offering a wide range of settings (power, voltage adjustments) and the option of using different resistance coils. The presence, number, and positioning of wicks are also important. Because they are closer to the mouthpiece than bottom coils, top coils deliver warmer vapors than bottom coils. More recently, wickless clearomizers have been marketed. These use a central cotton core to absorb the e-liquid and feed it to the heating coil. Several holes on the inner tube allow the e-liquid to flow easily through the clearomizer. These advanced technological devices may also contain a built-in electronic chip to adjust the voltage and power of the heating element, and an ohmmeter to measure the electrical resistance of the coil. Some clearomizers can be disassembled to remove and replace the atomizer and coil(s). A coil with another resistance can be fitted. At constant voltage, the lower the atomizer’s resistance, the greater the amount of aerosol generated. Each level of resistance also requires a certain voltage/power combination for optimal performance and vapor production. For a specific coil and resistance, the gradual increase in voltage progressively produces no, small, significant
Int. J. Environ. Res. Public Health 2015, 12 9991 and optimal amounts of warm vapors, or even hot smokes. Numerous websites and user forums report that, under optimal operating conditions (e.g., 3.7 V tension battery and 1.5–1.8 ohm resistance coil), power loads ranging between 8 and 9 watts are ideal for procuring large amounts of vapor, very pleasant sensations, and the typical throat hit that many users highly appreciate. This electric power setting was also considered as optimal and was selected by Farsalinos et al. (2014) for comparing the efficiency of nicotine delivery between first- and latest-generation e-cigs [6]. Developing on these features, several types of e-cigs were designed and adapted so as to be able to vape dry herbs, oil concentrates, or cannabis-based e-liquids as shown in Figure 2. The ability to regulate the evaporation temperature significantly raises the attractiveness of using e-cigs for vaping psychotropic drugs, such as (−)-trans-Δ9-tetrahydrocannabinol (THC), the main psychoactive cannabinoid in marijuana. In addition to THC, supposed treatments for various pathologies can now be bought from legal and illegal drug retailers, based on cannabinoids other than THC (e.g., cannabidiol, cannabigerol) [7,8], and could be administered by vaping through conventional e-cigs or very likely more efficiently with e-vaporizers. Recently, a special device was even patented to make e-cigs compatible for vaping nicotine [9], THC, tobacco, cannabidiol or alkaloids. Solowij et al. [10] reported optimized protocols for the delivery of cannabidiol, and combined cannabidiol and THC, by vaporization using a Volcano® table vaporizer (Storz & Bickel, Tuttlingen, Germany). In parallel with this, innumerable Internet forums describe attempts and failures to manufacture hash oil mixtures using tinctures or vegetable glycerol/propylene glycol or, less frequently, polyethylene glycols (mixtures of PEG 200, 300 and 400) that can be vaped as e-liquids in e-cigs. The fact to heat herb extracts at lower temperatures (140 °F –374 °F or 60 °C–190 °C) than combustion temperatures (1472 °F –1652 °F or 800 °C–900 °C) can still produce an inhalable vapor that can be vaped in e-cigs. Although the vapor thus contains smaller amounts of harmful pyrolyzed by-products, it still contains the psychoactive ingredients (e.g., nicotine, or cannabinoids from marijuana). Controversy continues surrounding the real or supposed benefits and risks of e-cigs that deliver nicotine vaporized from enriched e-liquids [5], particularly among youth [4], yet other issues also deserve attention. To assess the different options available for vaping cannabinoid aerosols using e-cigs, a short literature review was carried out. This review is intended primarily for medical staff involved with cannabis-related health issues as this target audience is generally misinformed about the possible uses of e-cigs for vaping cannabis extracts, as well as how e-cigs work. Forensic scientists will also benefit from this review. The different types of e-liquids and the various manufacturing methods for preparing cannabis concentrates are described in order to improve understanding of the various ways of using e-cigs for marijuana inhalation. The review concludes with a discussion on the respective advantages and disadvantages of regular cannabis joints and e-cigs, including the underlying major health risks and safety hazards of vaping for youths, teenagers, and non-smokers. Some recommendations for mitigating public health risks are also proposed. Because of the paucity of the available scientific data regarding cannabis and vaping, we often had to rely on information about nicotine vaping, which has been more thoroughly examined for many of these aspects. For the same reason, the review took account of the very rich underground literature and presented some original experimental results from our laboratory on a cannabidiol-enriched e-liquid and on cannabis butane honey oil concentrate (BHO).
Int. J. Environ. Res. Public Health 2015, 12 9992 Figure 2. Some models of e-cigs for vaping (a) ground marijuana head tops; (b) cannabis wax (butane honey oil concentrate (BHO)), or (c) cannabis e-liquid. The letters a, b, or c after the numbers indicate the parts of e-cigs used for herb, BHO, or e-liquid vaping, respectively. 1. Mega electronic cigarette (e-cig) with dual-coil clearomizer, adjustable airflow control ring, changeable resistance coils and high capacity, variable voltage battery. 2–7. Dry herb and wax vaporizer: 2. Spring-loaded mouthpiece; 3. Vaporizer chamber; 4. Dry herb coil head; 5. Wax coil head; 6. Detachable base with air holes; 7. Medium capacity battery. 8–10. See-through clearomizer for e-liquids: 8. Clearomizer tip; 9. Clearomizer tube; 10. Clearomizer coil and four-wick head with base assembly. 11–14. Glass-globe atomizer wax tank: 11. Drip tip; 12. Glass globe; 13. Ceramic heating chamber and coil; 14. Metal core. 15–19. Dry herb atomizer: 15. Soft drip tip (mouthpiece); 16. Ceramic screen; 17. Metal screen and spring; 18. Screens connector; 19. Ceramic chamber and battery connector. 20. Medium size battery. 21–22. Wax coil head atomizer: 21. Metal mouthpiece and wax coil chamber connector; 22. Wax coil ceramic chamber and battery connector. 23–25. Clearomizer for e-liquids: 23. Shell (mouthpiece attached to metal tank with viewing window); 24. Bottom head changeable coil assembly; 25. Battery base connector. a. Marijuana head tops, b. Cannabis Butane Honey Oil concentrate (BHO), c. Cannabis e-liquid (mixture of cannabinoid concentrates (cannabis wax), propylene glycol and glycerol).
Int. J. Environ. Res. Public Health 2015, 12 9993 2. Literature Search Systematic literature searches were conducted using the PubMed, Web of Science, Google Scholar, and Embase databases, using the following set of relevant search terms: (“electronic cigarette” OR “e-cigarette” OR “e-liquid”) AND (“cannabis” OR “marijuana”). The regular Google search engine and grey literature (e.g., ref. [11]) were also consulted. The literature search covered 2003 to July 2015; 2003 corresponds to the development of the first e-cigs by Hon Ilk, in China. 3. Vaporized Material 3.1. Context A synthesis of the practical recipes and experiments reported on the Internet (in addition to our own experiments) shows that the simple, direct use of purified cannabis extracts in e-cigs is not easy because cannabinoids are poorly soluble in e-liquids. Indeed, used pure or in mixture with glycerol, the propylene glycol (PG, or propane-1,2-diol) that is commonly used in e-liquids has both hygroscopic and hydrophilic properties. Consequently, it is not miscible with mineral and vegetable oils and fats. In contrast, cannabinoid concentrates are very lipid soluble, but water insoluble. Furthermore, PG, glycerol, terpenoids, plant fats and waxes, cannabinoid concentrates and THC are very viscous substances. Accordingly, the manufacture of a homogeneous solution using these viscous liquids is a tedious task. Cannabinoid concentrates resemble more a thick, sticky, gummy resin than a liquid. We can infer from these facts that they do not mix readily with glycols, and even less so with glycerol. The addition of terpenoids (e.g., limonene) or lecithin has been advocated to help make cannabis oils miscible [12]. Adding flavors (e.g., menthol, tobacco, orange crush) with a fragrant aroma to e-liquids can mask the typical, strong odor of cannabis drugs and make it less detectable. Although glycerol and propylene glycol are not ideal solvents for dissolving cannabinoids, propylene glycol is an excellent emulsifier and can be used to make e-liquids, such as (BHO)-PG emulsions. To do this, BHO is dispersed in PG solution using a modular high-speed homogenizer drive-unit equipped with a dispersing shaft (such as an Ultra-Turrax blender, IKA, Germany). The main problem with emulsions is that they are not often fully stable, and after a length of time they tend to separate progressively into two phases [13]. The separated BHO droplets may also stick to various parts of the e-cig, such as the tank walls or the wicking elements. The inhomogeneity of e-liquid could be a further problem: a particulate phase, made up of fine debris of plant tissues and trichomes, can coexist with the emulsion. A significant part of the cannabinoids can be contained in the trichomes or adsorbed on cellular debris. These insoluble materials can damage or impede the proper functioning of the atomizer. Just as with tobacco smoke, this particulate phase can be harmful to the lungs. Most of these problems can be prevented by performing intensive purification of the BHO (winterization and fine filtration), diluting it appropriately in glycols, and avoiding the use of glycerol. Exceeding a 1:2 w/w ratio between the purified BHO and the e-liquid (neat PG or mixture of glycols) usually leads to a phase separation [14].

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